Abstract: Mango fruits (cv. Chausa) were treated with different concentrations of CMC, calcium chloride and beeswax. The mangoes were then placed in boxes, each with a sponge soaked in KMnO4.The mangoes were then stored at refrigerated temperature (8-10°C). The physico-chemical analysis were repeated after seven days interval. Fruits treated with 2% CMC, showed best behaviour through out storage period with minimum loss of weight, increased ascorbic acid content and was able to conserve better sensory characteristics through entire period of storage.
INTRODUCTION
Mango is one the most popular and best loved fruit worldwide. Its popularity is because of its excellent flavour, attractive fragrance, beautiful colour, delicious taste and health giving properties. Ripe pulp of mangoes provides 74 kcal of energy per 100 g of edible portion (Salunkhe and Desai, 1984). It is second major fruit crop in Pakistan with the production of 1036 thousand tons (GoP, 2003) during the year 2002-2003 and contributing 5.86% of total worlds production of mangoes (Anonymous, 2001).
According to an estimate, about 35% of fruits and vegetables are wasted in Pakistan (Anonymous, 2001). Due to this wastage, mango growers are not in a position to supply high quality produce to market. It is important to reduce these losses, to maintain the freshness of fruit for distant local markets, export and to regulate fruit supply in the off-season.
Kent’ mango is one of the main mango cultivar commercialized in the world. Nevertheless its perishable character reduces its life of shelf. The objective of this research was to study the effect of different calcium applications, wax and combinations of both by the immersion method. The fruit were stored at 10°C for 30 days and soon transferred to 20°C for 12 days. Commercial-grade mangoes were treated hydrothermally and the following treatments were applied: control (T1); wax (T2); 0.5% CaCl2 (T3); 0.5% CaCl2+wax (T4); 1% CaCl2 (T5); 1% CaCl2+wax (T6). Respiration rate, general appearance and weight loss were evaluated daily, while firmness, pulp color, total soluble solids, pH, titratable acidity, calcium content in the peel and the pulp were determined at 3-day intervals. T3, T4, T5 and T6 increased the calcium content in the peel of the fruit, with values proportional to concentrations applied. In the pulp, the increase of the calcium content was smaller than ones in the peel. Treatment T6 fruit, compared with the other treatments, had significant differences in respiratory rate and weight loss, and had a good appearance, without spots and rots at the 12 days of the evaluation to 20°C (Bringas-Taddei et al., 2002).
Angeleno’ plums were coated with edible Hydroxypropyl Methylcellulose (HPMC)-beeswax (BW) composite coatings. The coatings consisted of beeswax at 4 lipid content levels (0, 20, 40 and 60% dry basis). One group remained uncoated as control and another group was dipped in water. Plums were stored 2, 4 and 6 weeks at 1°C and transferred to 20°C for 1 to 3 weeks. Weight loss, deterioration index and texture of plums were measured during storage. Sensory quality was also evaluated. No differences in weight loss were observed between uncoated and 0% BW-coated plums. Weight loss decreased as lipid content increased from 20 to 40%, but above 40% BW content, weight loss was not further reduced. Coatings improved texture compared with uncoated plums after prolonged storage at 1 and 20°C. No differences were observed in the deterioration index during treatments as storage time at 20°C increased for samples initially stored 2 weeks at 1°C. However, the deterioration index of coated samples stored 4 or 6 weeks at 1°C decreased compared with uncoated plums as storage time at 20°C increased. Flavor was not affected by coating application. Results indicate that HPMC-BW coatings have the potential to extend shelf-life of ’Angeleno’ plums held at 20°C (Navarro et al., 2004).
With the expansion of fruit processing industry, storage is becoming an important factor in the operation of the processing plant at uniform rate. To minimize wastage of fruits, remedy is to delay their ripening by storage (Nazri, 1981). Mango is a type of tropical fruit which is very perishable and it is necessary to keep it cool after harvest. Cold storage and application of skin coatings control the ripening process and reduce aging and water loss (Sundararaj et al., 1972) and have no doubt in increasing the shelf life of fruit.
Materials and Methods
Mango (Mangifera indica L.)
Fresh, unripe, hard and green mangoes (Mangifera indica L.) of variety
chausa were harvested from Multan (PUNJAB) orchards. Care should be taken that
all the mangoes were of same maturity level.
Hot Water Treatment
Mangoes after harvesting from orchards were immediately given hot water
treatment at 50°C for 3 min (Subramanyam et al., 1975) and then mangoes
were air dried to drain off any excess water.
Treatments
The mangoes were given different treatments including CMC (1, 2 and 3 %),
calcium chloride (1, 2 and 3%), beeswax (2%), polyethylene sheet and control
treatment.
Storage of Mangoes
The mangoes were then placed in boxes having holes at the front and both
sides. Also sponges soaked in saturated KMnO4 solution were placed
in boxes and mangoes were then stored at refrigerated temperature (8°C)
for 3 months (September to November) during the year 2003.
Evaluation of Mangoes
Mangoes were evaluated for different physico-chemical analysis after regular
interval of seven days for 3 months (September to November) during the year
2003.
Physical Analysis
Physical analysis includes weight loss, which was determined by using triple
beam balance. TSS were determined by using hand refractometer according to AOAC
method no. 932.12. pH was determined by using pH meter according to AOAC method
No. 981.12. (1990).
Chemical Analysis
Different chemical analysis includes titratable acidity, which was determined
according to AOAC method No. 942.15. Ascorbic acid was determined according
to AOAC method No. 967.21. (1990).
Sensory Evaluation
Samples were evaluated for colour, flavour, taste and texture by a panel
of five judges, using nine point hedonic scale as described by Larmond (1977).
Statistical Studies
Finally the data obtained for each parameter were subjected to statistical
analysis using the techniques of Steel and Torrie (1980).
Results and Discussion
Physical Analysis
Weight Loss
Data pertaining to weight loss indicated highly significant results and
showed a general trend of decrease in weight during storage. This was observed
for all the fruits, coated and the control ones. However, the rate of decrease
in weight was comparatively slower in coated fruits than in the control ones.
From the Table 1, it is evident that maximum score was recorded for control T0 (control) on 49th day of storage whereas minimum weight loss was recorded for T2 (CMC 2%) throughout storage period of 77 days, due to the presence of coating that act as semi permeable membrane and help in lesser loss of moisture (Lim et al., 1998).
| Table 1: | Effect of different treatments and storage intervals on weight
loss (%) |
| Total Soluble Solids (° brix) and pH of mango fruit during storage at refrigerated temperature | |
Total Soluble Solids
Data regarding total soluble solids revealed highly significant results
and there was a general trend of increase in TSS with time and then gradual
decrease for both coated and control fruits. Table 1 showed
that T4 (polyethylene sheet) have lowest value in terms of TSS and
proved to be poor in terms of TSS. Decrease in TSS might be the result of activities
of microorganisms causing the consumption of sugars. T2 (CMC 2%)
retained maximum TSS followed by T7 (calcium chloride 2%).
pH
The results regarding pH, as described in Table 1 were
highly significant and showed mixed pattern of increase and decrease in pH but
on the whole there was an increase in pH. Minimum value of pH was recorded for
T0 (control), followed by T4 (polyethylene sheet). Maximum
pH was recorded for treatment T2 (CMC 2%).
Chemical Analysis
Titratable Acidity
Titratable acidity initially decreased and then increased during storage
but the net result is decrease in acidity. Table 2 indicates
that minimum acidity was observed in T0 (control), also in T4
(polyethylene sheet) probably due to the fact that as fruit ripens it diminished
its malic and citric acid contents, due to microbial activity (Martinez et
al., 1997). Maximum acidity was observed in T2 (CMC 2%).
Ascorbic Acid
The results regarding ascorbic acid generally showed a gradual decline of
ascorbic acid with time. From Table 2 it is clear that minimum
ascorbic acid content were recorded for T0 (control) followed by
T4 (polyethylene sheet) probably due to increased respiration, causing
loss of ascorbic acid. Maximum ascorbic acid content was observed for T2
(CMC 2%) due to lesser loss of acid.
Sensory Evaluation
Skin Colour
The data regarding mean values of scores for skin colour of fruits stored
at refrigerated temperature indicated that there was a significant difference
among skin colour scores of different treatments. Generally increasing trend
in colour scores was observed and then at the end there was a decrease in the
scores. An experienced panel of judges carried out the evaluation of skin colour.
| Table 2: | Effect of different treatments and storage intervals on titratable
acidity |
| (Citric acid) (%) and Ascorbic Acid (mg/100 gm) of mango fruit during storage at refrigerated temperature | |
| Table 3: | Effect of different treatments and storage intervals on skin
colour, pulp colour and taste (scores) of mango fruit during storage at
refrigerated temperature |
| Table 5: | Effect of different treatments and storage intervals on flavour
and texture (scores) of mango fruit during storage at refrigerated temperature |
From Table 3 it is clear that T2 (CMC 2%) had best score for skin colour and it differed significantly with all other treatments. The appearance of skin colour is related to skin chlorophyll degradation. While control treatment in the absence of coatings was unable to give significant results.
Pulp Colour
Table 3 presents mean values of scores for pulp colour
of fruits stored at refrigeration temperature. The general trend was an increase
and then decrease in scores. Overall coated fruits produced significant results.
Comparison of the means of different treatments showed that maximum value for pulp colour of mangoes was recorded in T2 (CMC 2%), as ripening is up to the mark with appearance of more number of carotenoids (John et al., 1970; Katayama et al., 1971).
Taste
The data containing mean values of scores for taste of fruits stored at
refrigeration temperature is depicted in the Table 3, with
a general trend of an increase and then decrease in scores. From Table
3, it is evident that T5 (beeswax 2%) had minimum values for
taste scores, might be due to improper sugar to acid ratio. T2 (CMC
2%) had produced appreciable results for taste scores, due to increased sweetness.
Flavour
Data pertaining flavour, generally showed a gradual increase in flavour
scores followed by a gradual decline with the passage of time. The best ranking
was observed for T2 (CMC 2%), while lowest score for flavour was
recorded in T0 (control), T4 (polyethylene sheet) and
T5 (beeswax 2%), as it is clear from the Table 4.
Texture
Table 4 shows mean values of scores for textures of fruits
stored at refrigeration temperature with a general trend of an increase and
then decrease in the scores. Table 4 clearly indicates that
T2 (CMC 2%) had the most score for texture while control (T0)
had least score, due to the absence of coatings that help to maintain texture
of fruits by reducing the movement of water molecules into the cell and out
of the cell.